6. Simon the Sorcerer (GOG, $5.99)
Simon the Sorcerer is your standard point-and-click adventure game. You play as Simon, the unwilling, teenaged hero as he is transported into a fantasy world and must save the good wizard, Calypso, from the evil sorcerer. However, Simon is not your typical, dashing hero yearning only to do good and set things right. In fact, he's sort of a jerk. No, make that: A colossal jerk. He insults both friend and foe alike, and will often make a rather simple task increasingly complicated. This series is like Monkey Island meets Discworld, with just a dash of old-school graphics.
7. Spelunky (Spelunky World, Free)
Depending on your attitude toward spectacular failure, Spelunky (pictured) could either become your greatest pleasure or your chief torment - maybe even both. The vast cave system of Spelunky is unrelentingly cruel: You'll find yourself blocking arrows with helpless damsels and sacrificing fresh yeti corpses to an ancient god just to have a shot of making it to the final level. But you don't play Spelunky to feel like a hero; you play it to feel like an explorer. I've made over 600 trips into those infernal caves, and I still haven't seen everything. Not bad for a freebie.
8. Audiosurf (Steam, $9.99)
Audiosurf fuses standard color-matching gameplay with your Mp3 library, creating levels based on any song you give it: High-speed rock for an intense rush, quiet jazz for an easy and relaxed ride. It's almost infinitely replayable, it's a game that is literally tailored to your unique tastes, it makes listening to your favorite tracks an interactive experience, and it will set you back no more than $10.
9. Plants vs. Zombies (Steam, $9.99)
For years we've assumed that the most effective weapon for dealing with the undead would be a shotgun or, barring that, a chainsaw. But no, it turns out the most effective weapons for the undead are based in horticulture. A quirky and addictive tower defense game from PopCap, there's not much to say about PvZ that we haven't already: It's great, it has an awesome theme song, and it's just $10 on Steam. What are you waiting for, the actual zombie apocalypse?
10. Osmos (Hemisphere Games, $10)
Imagine you're a molecule, drifting languidly in a vast sea of other molecules. Your only task is to absorb other molecules to grow, and avoid being absorbed by larger molecules yourself. With such simple gameplay, controlling your molecule becomes a natural, organic experience, which allows you to become fully immersed in the ambient music and soothing visuals. It's meditation in game form. The developers claim that "good things will come to those who wait," so float around and see what happens by.